As the next generation systems to achieve higher-speed, larger-capacity communication than the 3rd and 3.5th generation cellular radio communication systems currently in use, there are LTE (Long Term Evolution) and LTE Advanced that is an enhanced version of LTE, which are standardized by the 3GPP (3rd Generation Partnership Project) being a standardization organization.
Meanwhile, there has been a plan to provide LTE Advanced with a heterogeneous network being a network in which low-power base stations (so-called pico-cell base stations, femtocell base stations, and the like) are placed within the communication area of a high-power base station (so-called a macro-cell base station). In a heterogeneous network, low-power base stations are placed within a high-traffic zone (so-called a hot zone), for example, thereby allowing distribution a load on a high-power base station to the low-power base stations.
However, radio terminals are generally configured to be connected to the radio base station providing a radio signal with the highest received power among multiple radio base stations. Thus, in a heterogeneous network, there is a possibility that radio terminals are less likely to be connected to a low-power base station with low transmission output.
In view of such circumstances, techniques have been proposed which involves such control that radio terminals are connected to a low-power base station even when the received power from this low-power base station is not the highest, thereby expanding the coverage (the range of the communication area) of the low-power base station (see Non-patent Document 1, for example).